Contents

Research

Project Overview

In many of the worlds oceans, currents carry debris and pollution originating from coastlines. This waste accumulates in regional gyres, where ocean currents meet, and can reach extremely high concentrations. Plastic is estimated to account for 60-80% of this debris, and is known to be gradually broken down by solar energy and the mechanical action of the sea. This means the majority of the plastic waste are several millimetres in size or less, which has made efforts to clean them from the ocean largely unsuccessful. These tiny plastic fragments - microplastics - enter the digestive systems of resident organisms, which are affected either by the physical size of the plastic or its toxicity from adsorbing organic pollutants.

UCL iGEM proposes a synthetic biology approach for the bioremediation of micro-plastic pollutants within the marine environment, with emphasis on regions of excessive debris accumulation, such as the North Pacific ‘garbage patch’.

We intend to engineer Escherichia coli and marine bacteria Roseobacter denitrificans & Oceanibulbus indolifex to degrade plastic, or aggregate it into islands.

Detection Module

Detection of plastics as a trigger for the Aggregation module

Our Detection module will allow our bacteria to detect the presence of plastic. This serves to control the production of our adhesive – curli fibrins – which binds non-specifically to an extraordinary array of surfaces. By producing adhesive only when plastic is present, we prevent our bacteria binding to non-plastic materials.

Aggregation Module

Curli expression for the aggregation of plastic and production of biofilm

The Aggregation Module confers onto our bacteria the means of plastic adhesion. To implement this we have decided to transform our bacteria with a genetic circuit to produce adhesive proteins called curlis. As curlis are non-specific in the surfaces they bind to, the Detection module will limit their production, unless they are in the presence of plastics.

Plastic Degradation

Multi-copper oxidase/Laccase for the degradation of polyethylene and other plastics

As an alternative to Island Formation Modules (Modules 1 and 2), we are also developing an alternative solution – Degradation of plastic. This will investigate enzymes expressed by numerous organisms that have been demonstrated to degrade plastics.

Buoyancy Module

Temperature dependent buoyancy for localisation of engineered bacteria within the water column

The Buoyancy Module is key to both the Degradation (Module 4) and the Island Formation systems (Module 1 and 2). Buoyancy is required to position our bacteria in the water column, alongside the plastic fragments, and also to enable them to buoy the plastic aggregates (Module 2).

Salt Tolerance

A core module for our project is enabling E.coli to tolerate the salt content of the ocean; without this ability E.coli could not survive in a marine environment. Due to the widespread use of E.coli as a chassis for Synthetic Biology this Module is being developed to demonstrate that E.coli, as well as marine bacteria, could be used as the chassis for this project.

Containment Components

A novel threefold active biological containment system

UCL iGEM 2012 addresses fundamental barriers to the implementation of traditional biological containment systems. As our project proposes the release of genetically modified bacterium into the environment, we feel it is necessary to contain the risk of spreading genetic information by horizontal gene transfer. To do so we are suggesting a multi-containment system, consisting of three toxin/anti-toxin pairs - Holin / Anti-Holin Endolysin, Colicin-E3 / Colicin Immunity E3, and Endunuclease EcoRI / Methyltransferase EcoRI. Our system will also have an exonuclease component.